DESCRIPTION: (Investigator's Abstract). Keratorefractive surgery changes refractive error by permanently altering the optical performance of the cornea. These new surfaces differ optically from their preoperative counterparts. Topography and psychophysical studies show clinically significant differences in structural stability, quality of resolution (central and peripheral vision), depth of field, reproducibility of clinical refraction, pupil effects on refractive error, and pupil effects on glare and blur in both the central and peripheral visual field. The severity of optical aberration will be exacerbated by inadequate preoperative screening for corneal disease. Any surgeon or design error will exacerbate the problem. Hundreds of thousands of Americans have had keratorefractive surgery. It seems logical to develop methods that measure the optical performance of the keratorefractive surface in as direct and accurate way as possible; and to try to correlate topography and psychophysical measurements with measurements of the optical performance of the cornea. Without this knowledge, it is impossible to assess whether iatrogenically induced corneal aberration from keratorefractive surgery will accelerate the onset of visual dysfunction from the two most common causes of visual loss in the aging population-cataract and age-related macular degeneration. To that end, we are developing a ray tracing system to model the optical performance of the cornea. This grant seeks to refine our model into a system that accurately assesses the optical performance of optically aberrated corneas. It will evaluate the precision of topography system the electronic optical bench uses to describe the lends characteristics of the cornea; improve and validate the ray tracing algorithms the model uses to generate lens throughput from the corneal topography data; develop autofocus programs that identify along the optical axis the best resolved image generated by the ray tracing system; and apply the optical bench method to studies of keratorefractive surgery.